Influence of tribo-electrification on bulk powder rheology

Understanding and control of powder material properties and their influence on process operations are critical in manufacturing processes involving particulate solids. Powder handing is often accompanied by a significant potential for tribo-electrification, a phenomenon which adversely affects the ability to process powders with consistency. However, understanding of the impact of tribo-electrification on powder behaviour is very poor.
The Ghadiri Research Group at the University of Leeds have developed a number of measurement techniques for the characterisation of tribo-electrification, the latest development being around the use of the dispersion unit of the Malvern Panalytical Morphologi analysis system for tribo-electric charging, accompanied by a Faraday cage for charge measurement. However, almost all methods available are based on dispersed powders systems. Assessment of tribo-electrification of bulk powders under shear straining, as it occurs during powder flow, has not been widely addressed. It is a topic worthy of development and further understanding in view of its direct relevance to industrial applications in powder handling.
This project seeks to develop appropriate experimental tools and associated analysis to evaluate the response of a wide range powder systems. The project therefore clearly aligns with the aims of the CDT to look at relationships between materials, processes and performance in the field of powder research.

Aims
1. Consider various techniques relevant to understanding the tribo-electrification of powder systems;
2. Develop appropriate techniques to characterise tribo-electrification of bulk powders
3. Validate the measurement accuracy and parameter space for various techniques;
4. Develop models linking particle size, shape and electrostatic charge and the impact these have on powder processability.

The establishment of a CDT in Complex Particulate Products and Processes will have a range of positive impacts, both academic and socio-economic. We identify four groups of beneficiaries: industry partners and associated supply chains; academia; the general public; and government policy makers.

The research undertaken within the CDT will have a strong links to current UK industry needs. Particle science and engineering underpins a wide-range of manufacturing sectors in the UK including foods, home & personal care, healthcare, pharmaceuticals, agrochemicals, fine chemicals, catalysts and coatings. The CDT will support a highly significant part of the UK manufacturing base; a UK strategic sector that provides direct employment for 214,000 people and supports several hundred thousand additional jobs throughout the economy [UK Trade and Industry Report 2009: Chemicals - the UK advantage: Adding value for global investors and industry].

Clearly, the research outputs of 50 strategically-focused PhD research projects will significantly enhance knowledge in the area that will be proactively transferred to industry. Given our normal expectations, many of the CDT projects will lead to high-quality papers in the scientific literature thereby advancing our scientific and engineering understanding and providing impact within the academic community. It is also a key aim of the CDT to work across the boundary of science and engineering with a focus at the chemistry/chemical engineering interface. This is an area of current need and has been highlighted in a number of reports for investment, most recently the EPSRC Review of the Chemistry/Chemical Engineering Interface 2010/11. A CDT at this interface will build innovative approaches to integrated training where graduates are comfortable with the 'whole process', notably the impact that "small" decisions taken in product design can have on the efficiency and sustainability of manufacturing processes.

Moving beyond the traditional disciplinary boundaries and conventional research training approach, we will actively build teams clustered in a target area as is done in industry. For example, linking PhD projects on particle design, product stability and process development. Working together, the students can build a shared understanding of upstream and downstream process opportunities as well as understand any limitations that will ultimately affect the adoption of their research. This will have positive benefits for UK based industry, providing research leaders capable of driving innovation and creativity in this critical industry sector. Ultimately, there will also be benefits that accrue to the general public through the enhanced competitiveness of this critical manufacturing sector to the UK economy.

There is a need for graduates who understand how changes in ingredient quality, particle properties and/or formulation of a product can affect its processing and manufacturing. This links to the TSB high-value manufacturing strategy to apply 'leading-edge technical knowledge' to the 'creation of products' underpinning a technology-led economy where 'innovation in manufacturing' is a central theme. This addresses a government strategic agenda. The shortage of highly trained researchers to support novel and sustainable manufacturing approaches in this area has also been explicitly noted from our survey of 20 major manufacturing companies, highlighting a difficulty in finding engineers and scientists with the necessary skills. Across this space, there is a strong requirement for engineers and physical scientists who can iteratively translate novel materials discovery through the design and development of viable manufacturing processes, into innovative high-quality products. The graduates from this CDT will have a significant impact on the industrial and academic research and development capacity in this important area as the next-generation of research leaders in the field.